Questions EndPoint Fun

Hi All,
I'm having a bit of trouble with endpoints and the customer name. I'm hoping all of these issues are related and I'm just missing something.

1. If I extend the SalesOrder end point to include CusName - ( Mapped Object: Order Summary, Mapped Fields: Order Nbr. -> Customer Name)
And then if I run a get for the endpoint, it pulls out an array that includes all of the sales orders. I can filter based on any field, except the customer name. When I try to filter on the customer name - /SalesOrder?$filter=CusName%20eq%20%27NIH%27

I get this error - 

"message": "An error has occurred.",
"exceptionMessage": "Invalid column name '[SOOrder].[CuryPaymentTotal]'\r\nInvalid column name '[SOOrder].[PaymentTotal]'\r\nInvalid column name '[SOOrder].[CustomerID__BAccountR__acctCD]'\r\nInvalid column name '[SOOrder].[CustomerLocationID__Location__locationCD]'\r\nInvalid column name '[SOOrder].[ProjectID__PMProject__contractCD]'\r\nInvalid column name '[SOOrder].[DestinationSiteID__INSite__siteCD]'\r\nInvalid column name '[SOOrder].[Document_NoteText]'\r\n",

(the error goes on for awhile)

So... I tried making a new endpoint. To start, I made a GI that just shows a few SOs. But when I tried to extend the endpoint to the GI, I get this error when I get the endpoint . -

"message": "An error has occurred.",
"exceptionMessage": "Optimization cannot be performed.The following fields cause the error:\r\nCustomerID: View Results has BQL delegate\r\n",
"exceptionType": "PX.Api.ContractBased.OptimizedExport.CannotOptimizeException",

Any ideas on either of these? 
We have 10 mbs of sales data and I'm trying to only pull what I need.

Thanks,
Matt